1. Field Of The Invention
The present invention relates to a process for the production of a composite material part of the carbon-carbon type, as well as to the parts obtained by this process. In particular, these parts are brake disks intended for use on land vehicles, aircraft, or space vehicles (rockets or shuttles). More specifically, the invention is applicable to all types of parts in which carbon-carbon plays a structural part.
2. Description Of The Background
A composite material of the carbon-carbon type is a material formed from a substrate of carbon reinforcing fibres, embedded in a graphite or carbon matrix.
These composite materials are obtained by densification of a porous substrate consisting either of impregnating the structure to be densified with a liquid hydrocarbon or a resin and then pyrolyzing the hydrocarbon or resin so as to obtain a coke matrix, or placing the substrate to be densified raised to an adequate temperature in a carbon-containing gas flow in order to thermally decompose said gas into pyrolytic graphite or carbon, which can then be deposited within the substrate.
Unfortunately, these densification processes are relatively long and therefore expensive. In connection with the vapour phase process (CVPD), this is linked with the difficulty of being able to make the gas to be pyrolyzed penetrate the interior of the porous substrate, said difficulty increasing with the thickness of the part. In addition, the lower the poroursity of the substrate, the more difficult it is to achieve the penetration of the carbon-containing gas. This penetration difficulty of the gas to be pyrolyzed leads to parts having a relatively ununiform density.
For the liquid impregnation method, the length of the process is due to the need to recommence the impregnation cycle several times.
The porous substrate to be densified is produced by unidirectional or multi-directional weaving, the holes possibly formed during weaving needle felting serving solely for the passage of the carbon reinforcing fibres of the composite material.
Moreover, it is known that brake disks produced from a homogeneous material, generally metal, have a plurality of holes oriented in accordance with the axis of revolution of the disk in order to aid braking under trickling water and cooling in general. These holes are obtained by drilling the disk following the production of the latter.
FR-A-2,144,329 in particular teaches the drilling of holes in a brake blank, following densification by immersion in a liquid resin, with a view to evacuating the gases formed during the carbonization of the resin. The sole function of these holes is then that of vents, which have long been known in conventional foundry methods.
GB-A-2 028 230 also teaches the drilling of holes in already densified fibre layers, with a view to the introduction of other fibres into them.